Presensitized deep etch lithographic plates



United States Patent Ofiice 3,348,948 Patented Get. 24, 1967 3,348,948PRESENSITIZED DEEP ETCH LITHOGRAHIC PLATES Robert F. Leonard, EastRockaway, and Madeline Beckett,

Hempstead, N.Y., assignors to Litho Chemical 8; Supply Co., 1nd,Lynhrook, N.Y., a corporation of New York No Drawing. Filed Mar. 11,1964, Ser. No. 351,219 12 Qlaims. (Cl. 96-75) This invention relates todeep etch lithographic plates which are presensitized and which retaintheir photographic sensitivity when stored for a prolonged period oftime as well as to procedure for the preparation of such presensitizeddeep etch lithographic plates and more particularly to the use of acoating on at least one surface of such plates of adiazido-polyvinylpyrrolidone sensitizer.

The deep etch lithographic process is per se well known and is describedin Publication No. 806 of The Lithographic Technical Foundation, Inc.(1954). It is also known that polyvinylpyrrolidone has been used inconjunction with diazonium sensitizers but has been found to beunsatisfactory as a deep etch resist because of the solubilitycharacteristics of polyvinylpyrrolidone both in water and in organicsolvents. This serious disadvantage has been obviated by the presentinvention wherein the polyvinylpyrrolidone is combined with polyacrylicacid or with other substances as hereinafter more fully set forth suchas resorcinol or tannic acid. This combination is used in conjunctionwith the sodium salt of 4,4-diazidostilbene-2, 2'-disulfonic acid whichis converted into its tetrazo form by means of sodium azide. Thus, inaccordance with the present invention, a number of differentformulations may be employed as diazido-polyvinylpyrrolidone basedsensitizers. Four typical and entirely satisfactory formulations are asfollows:

Formulation 1: Percent Water (distilled) 94.25 Polyvinylpyrrolidone K-904.09 Polyacrylic acid (M.W. 95,000) 0.23

Sodium salt of 4,4-diazidostilbene-2,2-disulfonic acid 0.9-1 Sodiumazide 0.30 Wetting agent 0.22

Formulation II:

Water (distilled) 93.19

Formulation IV:

Water (distilled) 93.67

Polyvinylpyrrolidone K-90 4.50 Tannic acid 0.25 Sodium salt of4,4'-diazidostilbene-2,2'-disulfonic acid 1.00 Sodium azide 0.33 Wettingagent 0.25

Any suitable wetting agent can be employed, but it has been found thatoctyl phenoxypolyethoxy ethanol with an ethoxy chain length of 9 to 11carbon atoms is particularly suitable and eifective, and this wettingagent is available commercially as Triton X-100.

It is also pointed out that the proportions of ingredients in the aboveformulations are of critical significance and cannot be varied more than-l0% from the amounts specified above and that departures from theformulations of more than such permissible tolerance renders theformulations unsatisfactory or ineffective. This permissible variationapplies to each ingredient individually. Each of the above formulationscan be used to presensitize deep etch lithographic plates and thethus-produced plates retain their photographic sensitivity or solubilitywithout undergoing any appreciable adverse change. Each of theformulations can be applied to various deep etch lithographic platessuch as aluminum plates, zinc plates, magnesimum plates, stainless steelplates, copper electroplated aluminum bimetal plates, copperelectroplated stainless steel bimetal plates, chromium electroplatedcopper bimetal plates, aluminum trimetal plates electroplated first withcopper and then With chromium, and mild steel trimetal plateselectroplated first with copper and then with chromium.

The above sensitizer formulations can be used interchangeably in all thesucceeding examples without adversely affecting the qualities andperformance of the presensitized plates. It is also to be understoodthat while the examples employ the whirlcoat method of application, theinvention is not limited to any specific method of applying thesensitizers since it has been found further, for example, that adraw-down blade or a curtain coater can be equally well employed toapply the sensitizer to any of the above-noted plate surfaces.

Presensitized plates according to the present invention have been foundto have a minimum storage life of at least six months and no maximumstorage life has yet been encountered. Some plates were presensitizedfor eighteen months before final processing. This is, an importantcommercial and operational advantage not shared by known presensitizedplates. The presensitized plates .of this invention have the furtheradvantage over conventional lithographic plates in that the so-calledcontinuing dark reaction is absent, this being the name given to theeffect of continued insolubilization of a lightsensitive coating aftertermination of exposure. The continuing dark reaction effect preventsthe exposing of portions of a conventional lithographic plate ondifferent days and obtaining the same degree of insolubilization overthe entire plate surface. In contrast, the pr sensitized plates of thepresent invention do not undergo the continuing dark reaction and thisis especially important in step and repeat work inasmuch as nocompensation has to be made in the exposure from the beginning to theend of the procedure. It will further be appreciated and understood thatthe present invention represents a marked and substantial advance in theart even though it includes certain phases of the invention of UnitedStates Patent No. 3,118,765.

The polyvinylpyrrolidone used has a K value between 88 and 94 andpolyvinylpyrrolidone K-90 is particularly suitable in the presentinvention. The K values assigned to various grades ofpolyvinylpyrrolidone represent a function of the mean molecular weightand, for instance, polyvinylpyrrolid-one K-90 has an average molecularweight of 360,000.

The polyacrylic acid is commercially available under the name Good-Rite(K-702 Polymer) and is a 25% aqueous solution of polyacrylic acid, whichsolution has a viscosity of 500 to 1200 centipoises, a specific gravityof 1.09, a pH value of 2 to 3, and a molecular weight in the range of90,000 to 100,000 given above as 95,000.

The diazoniumsensitizer is the sodium salt of 4,4-diazidostilbene-2,2-disulfonic acid produced by diazotizing4,4'-diaminostilbene-2,2'-disulfonic acid and then neutralizing thereaction product with sodium carbonate. Sodium azide is then'added toproduce the tetrazo form of the above compound and this has theimportant significance of increasing the hardening action of the diazocompound upon the polyvinylpyrrolidone-polyacrylic acid admixture orreaction product or on the admixture or reaction product ofpolyvinylpyrrolidone with resorcinol or tannic acid. The tannic acidmay, in addition, be utilized in conjunction with bothpolyvinylpyrrolidone and polyacrylic acid or the resorcinol or tannicacid may replace the polyacrylic acid.

The invention is illustrated by the following nonlimitative examples.

Example 1 A 17" x 22" x 0.012" sheet of ball grained 2S alloy aluminumis counteretched witha dilute :aqueous solution of acetic acid and thenrinsed thoroughly with tap water. The aluminum sheet is whirl coatedwith the. deep etch positive sensitizer of formulation I above usingconventional equipment and procedure. The sheet, after having beenwhirled dry, is exposed to a 13-amp. single carbon arc lamp at adistance of 40 inches for five minutes through a photographic positive.The sheet is then developed with the following developing solution whichselectively dissolves the non-light struck portions of the coating:

Grams Water 32.88 CaCl "13.78 ZnCl 11.85 Hydroxyacetic acid (100%) 1.64Ethylene glycol 38.84

CaCl solution aqueous (4041 B.) ml 1000* ZnCl grams 380 FeCl solutionaqueous (50-51 B.) ml.. 285 HO] solution (37-38%) aqueous ml 14 CuCl21-1 27 The sheet is next washed With 99% isopropyl alcohol to removethe etching solution after the desired depth of etch has been reached.The plate is now treated witha solution which will chemically depositcopper metal onto the bare etched image areas. The composition of such acopperizing solution is:

grams Isopropyl alcohol (99%) "ml" 1000 Cuprous chloride (Cu cl grams 31HCl (37-3s.5% ml 32 The plate is again flushed with 99% isopropylalcohol to remove the copperizing solution and to assist in removingmoisture from the sheet surface which is fanned dry.

Next the sheet is coated with any of the commercial non-blinding deepetch lacquers which are usually vinyl based. The lacquering step isfollowed by an inking step which comprises coating the plate with alayer of commercial developing ink. The purpose of this step is to makethe image apparent and to protect the lacquer layer from chemicalattach. The plateis then flushed with warm water and brushed lightly toremove the resist and the lacquer and ink adhering thereto.

Thereafter the plate is desensitized by coating with a solution ofphosphoric acid and gum arabic and when dried, moistened and inked, itis ready for printing.

Example 2 A 17 X 22" X 0.009" sheet of ball grained zinc iscounteretched with a dilute aqueous solution of hydrochloric acid, thenrinsed thoroughly with tap water. The Zinc sheet is whirl coated withthe deep etch positive sensitizer of Formulation I above, usingconventional equipment and procedure. The sheet, after having beenwhirled dry, is exposed to a 13 amp. single carbon arc lamp at adistance of 40 inches for five minutes through a photographic positive.The sheet is then developed with the following developing solution whichselectively dissolves the non-light struck portions of the coating.

Grams Water 32.88 CaCl 13.78 ZnCl 11.85 Hydroxyacetic acid 1.64 Ethyleneglycol 39.84

The spent developing solution is removed from the plate withsimultaneous removal of unhardened portions of the coating after whichthe plate is ready for deep etching. The etching of the plate isaccomplished by treating the unprotected portions thereof with thefollowing etching solutions:

The sheet is next washed with 99% isopropyl alcohol to remove theetching solution after the desired depth of etch has been reached. Theplate is now treated with a solution which will chemically depositecopper metal onto the bare, etched image areas. Thecomposition of such acopperizing solution is:

Isopropyl alcohol (99%) ml 1000 Cuprous chloride (Cu Cl grams 31 HCl(37-38%) aqueous solution ml 32 The plate is again flushed With 99%isopropyl alcohol to remove the copperizing solution and. to assist inremoving moisture from the sheet surface which is fanned dry.

Next, the sheet is coated with any of the commercial non-blinding deepetch lacquers which are usually vinyl based. The lacquering step isfollowed by an inking step which comprises coating the plate with alayer of commercial developing ink. The purpose of this step is to makethe image apparent and to protect the lacquer layer from chemicalattack. The plate is then flushed with warm water and brushed lightly toremove the resist and the lacquer and ink adhering thereto.

Thereafter, the plate isdesensitized by coating it with a solution ofphosphoric acid and gum arabic and when dried, moistened and inked, itis ready for printing.

Example 3 A 10" x 15" x .020" sheet of magnesium is counteretched with a5% aqueous solution of ammonium bichromate and pumice powder, thenrinsed thoroughly with tap water. The magnesium sheet is whirl coatedwith the sensitizer of Formulation IV using conventional equipment andprocedure. The sheet, after having been whirled dry, can be stored awayfor several months without any loss of photographic sensitivity or it isexposed to a 35 amp. double carbon arc lamp at a distance of 42 inchesfor five minutes through a photographic positive. The sheet is thendeveloped with the following developing solution which selectivelydissolves the non-light struck portions of the coating and also etchesthe bared magnesium:

p The sheet is next washed with 99% isopropyl alcohol to remove theetching solution after the desired depth of etch has been reached.

Next, the dry plate is coated with any of the commercial non-bindingdeep etch lacquers which are usually vinyl based. The lacquering step isfollowed by an inking step which comprises coating the plate with alayer of commercial developing ink. The plate is then flushed with warmwater and brushed lightly to remove the resist and the lacquer and theink adhering thereto.

Thereafter the plate is desensitized by coating with a solution ofphosphoric acid and gum arabic and when dried, moistened and inked, itis ready for printing.

Example 4 A 19%" X 23" X .015" sheet of ball grained 316 stainless steelis counteretched with a dilute aqueous solution of hydrochloric acid,then rinsed thoroughly with tap water. The stainless steel sheet iswhirl coated with the sensitizer of Formulation II, using conventionalequipment and procedure. The processing of the plate was carried out inthe same manner as in Example 2 with the exception that the copperizingsolution is of the following composition:

'Isopropyl alcohol (99%) cc 450 Ethylene glycol cc 450 Hydrochloricacid(37%) cc 42 Cuprous chloride grarns 32 Example5 A 20 x 22%" x .012"sheet of 0.0119 inch aluminum with a surface of 0.0001 inchelectroplated copper is counter-etched with a dilute aqueous solution ofsulfuric acid, then rinsed thoroughly with tap water. The copperelectroplated aluminum sheet is whirl coated with the Water' Cc 32.88CaCl grams 13.78 ZnCl do 11.85 Hydroxyacetic acid (100%) do 1.64Ethylene glycol do 39.84

The spent developing solution is removed from the .plate withsimultaneous removal of unhardened portions of the sensitizer, afterwhich the plate is ready for etching. The etching of the plate isaccomplished by treating the unprotected portions thereof with thefollowing etching solution which removes the hated copper but does notetch the underlying aluminum:

Ferric nitrate grams 640 Water cc 500 The plate is next flushed withwarm water and brushed lightly to remove the resist from the copperareas of the plate. The plate now consists of aluminum non-printingareas which were not exposed to light and copper image areas which wereprotected during the etching step by the light-hardened sensitizer.

Thereafter the aluminum surface is desensitized by coating it with adilute solution of gum arabic while the copper surface is made inkreceptive by application of a dilute aqueous solution of sulfuric acid.The inked and desensitized plate is now ready for printing.

Example 6 Example 5 was followed except that the plate consists of0.0001 inch copper electroplated directly on 0.0119 inch mild steel. Thechemical solutions and procedure used are the same except for theetching solution which has the following composition:

Ferric chloride grams 1000 Calcium chloride do 1000 Water cc 2000Example 7 A 10" x 15" x .009" sheet of .00895 copper with anelectroplated surface of .00005 inch chromium is counteretched with adilute aqueous solution of phosphoric acid, then rinsed thoroughly withtap water. The chromium electroplated copper sheet is whirl coated withthe sensitizer of Formulation II using conventional equipment andprocedure. The sheet, after having been whirled dry, can be stored awayfor several months without any loss of photographic sensitivity or itcan be exposed immediately to a amp. single carbon arc lamp at adistance of 52 inchcs'for five minutes through a photographic positive.The sheet is then developed with the following developing solution whichselectively dissolves the non-light struck portions of the sensitizer:

Water cc 32.88 CaCl "grams" 13.78 ZnCl do 11.85 I-Iydroxyacetic acid do1.64 Ethylene glycol do 39.84

The spent developing solution is removed from the plate withsimultaneous removal of the unhardencd portions of the coating, afterwhich the plate is ready for etching. The etching of the plate isaccomplished by treating the unprotected portions thereof with thefollowing etching solution which removes the bared chromium but does notattack the underlying copper:

Aluminum chloride, anhydrous grams 450 Zinc chloride do 630 Phosphoricacid (85%) cc 40 Water cc 700 The plate is next flushed with warm waterand brushed lightly to remove the exposed sensitizer from the chromiumareas of plate which will become the non-printing areas of the plate.The copper or printing areas of the plate consists of those areas whichwere not exposed to light and subsequently were etched free of chromium.

Thereafter the chromium surface is desensitized by coating it with adilute solution of gum arabic while the copper surface is made inkreceptive by applications of a dilute aqueous solution of sulfuric acid.The inked and desensitized plate is now ready for printing.

Example 8 A 19% x 23" x .012" trimetal plate composed of an aluminumbase 0.012 inch thick electroplated with 0.0001 inch of copper which iselectroplated with 0.00005 inch of chromium is sensitized and processedin the same manner as the plate of Example 7.

Example 9 A 20" x 22%" x .012" trimetal plate composed of a mild steelbase 0.012" thick electroplated with 0.0001 inch of copper which iselectroplated with 0.00005 inch of chromium is sensitized and processedin the same manner as the plate of Example 7.

What is claimed is:

1. A presensitized deep etch lithographic plate which retains itsphotographic sensitivity when stored for a prolonged period of time,comprising a metal plate having on at least one surface thereof acoating of a diazidopolyvinylpyrrolidone sensitizer composed of thefollowing constituents in the following amounts with in a L10%tolerance:

Percent Water (distilled) 93.19 Polyvinylpyrrolidone K-90 4.47Polyacrylic acid (M.W. 95,000) 0.51 Tannic acid 0.25

Sodium salt of 4,4'-diazidostilbene-2,2'-disulfonic acid 0.99 Sodiumazide 0.33 Wetting agent 0.25

2. A presensitized deep etch lithographic plate which retains itsphotographic sensitivity when stored for a prolonged period of time,comprising a metal plate having on at least one surface thereof acoating of a diazido-polyvinylpyrrolidone sensitizer composed of thefollowing constitutents in the following amounts within a :10% to1erance:

Percent Water (distilled) 94.22 Polyvinylpyrrolidone K-90 3.92Resorcinol 0.22

Sodium salt of 4,4-diazidostilbene-2,2-disulfonic acid 0.87 Sodium azide0.33 Wetting agent 0.22

3. A presentized deep etch lithographic plate which retains itsphotographic sensitivity when stored for a prolonged period of time,comprising a metal plate having on at least one surface thereof coatingof a diazido-polyvinylpyrrolidone sensitizer composed of the followingconstituents in the following amounts within a i10% tolerance:

Percent Water (distilled) 93.67 Polyvinylpyrrolidone K-90 4.50 Tannicacid 0.25

Sodium salt of 4,4-diazidostilbene-2,2'-disul fonic acid 1.00 Sodiumazide 0.33 W tting agent 0.25

4. A presentized deep etch lithographic plate according to claim 1, inwhich the metal of the plate is selected from the group consisting ofaluminum, zinc, magnesium, stainless steel, copper electroplatedaluminum, copper electroplated stainless steel, chromium electroplatedcopper, aluminum electroplated first with copper and then with chromiumand mild steel electroplated first with copper and then with chromium.

5. A presensitized deep etch lithographic plate according to claim 2, inwhich the metal of the plate is selected from the group consisting ofaluminum, zinc, magnesium,

7. A presensitized deep etch lithographic plate according to claim 1, inwhich the wetting agent is octyi phenoxy polyethoxy ethanol with anethoxy chain length of 9 to 11 carbon atoms.

8. A presensitized deep etch lithographic plate according to claim 2, inwhich the wetting agent is octyl phenoxy polyethoxy ethanol with anethoxy chain length of 9 to 11 carbon atoms.

9. A presensitized deep etch lithographic plate according to claim 3, inwhich the wetting agent is octyl phenoxy polyethoxy ethanol with anethoxy chain length of 9 to 11 carbon atoms.

10. A diazido-polyvinylpyrrolidone sensitizer for the production ofpresensitized deep etch lithographic plates, in which the sensitizer iscomposed of the following constituents in the following proportionswithin a 110% t0lerance:

Percent Water (distilled) 93.19 Polyvinylpyrrolidone K- 4.47Poly-acrylic acid (M.W. 95,000) 0.51 Tannic acid 0.25

Sodium salt of 4,4'-diazidostilbene-2,2'-disulfonic acid 0.99 Sodiumazide 0.33 Wetting agent 0.25

11. A diazido-polyvinylpyrrolidone sensitizer for the production ofpresensitized deep etch lithographic plates, in which the sensitizer iscomposed of the followingconstituents in the following proportionswithin a i10% tolerance:

Percent Water (distilled) 94.22 Polyvinylpyrrolidone K-90 3.92Resorcinol 0.22 Sodium salt of 4,4-diazidostilbene-2,2'-disulfonic acid0.87 Sodium azide 0.33 Wetting agent 0.22

12. A diazido-polyvinylpyrrolidone sensitizer for the production ofpresensitized deep etch lithographic plates, in which the sensitizer iscomposed of the following constituents in the following proportionswithin a tolerance:

Percent Water (distilled) 93.67 Polyvinylpyrrolidone K-90 4.50 Tannicacid 0.25

Sodium salt of 4,4-diazidostilbene-2,2-disulfonic OTHER REFERENCES Mees,Kenneth, C. -E., The Theory of the Photographic Process, McMillan Co.,N.Y., 1954, TRI45M4t, (pp. 5 805 82 relied on) (Copy in Group NORMAN G.TORCHlN, Primary Examiner.

C. L. BOWERS, JR., Assistant Examiner,

1. A PRESENSITIZED DEEP ETCH LITHOGRAPHIC PLATE WHICH RETAINS ITSPHOTOGRAPHIC SENSITIVITY WHEN STORED FOR A PROLONGED PERIOD OF TIME,COMPRISING A METAL PLATE HAVING ON AT LEAST ONE SURFACE THEREOF ACOATING OF A DIAZIDOPOLYVINYLPYRROLIDONE SENSITIZER COMPOSED OF THEFOLLOWING CONSTITUENTS IN THE FOLLOWING AMOUNTS WITH IN A $10%TOLERANCE: PERCENT WATER (DISTILLED) 93.19 POLYVINYLPYRROLIDONE K-904.47 POLYRACRYLIC ACID (M.W. 95,000) 0.51 TANNIC ACID 0.25 SODIUM SALTOF 4,4''-DIAZIDOSTILBENE-2,2''-DISULFONIC ACID 0.99 SODIUM AZIDE 0.33WETTING AGENT 0.25